FeCo / ZSM-5 catalyst as well as preparation method and application thereof

Abstract

The invention discloses a FeCo / ZSM-5 catalyst as well as a preparation method and application thereof. According to the catalyst, a ZSM-5 molecular sieve with a specific silica-alumina ratio is used as a carrier, and active components of iron (Fe) and cobalt (Co) are loaded. The preparation method comprises the following steps: dissolving an iron source and a cobalt source in an alcohol solvent, adding the ZSM-5 molecular sieve, carrying out ultrasonic-assisted impregnation, drying, grinding and carrying out high-temperature roasting in an inert atmosphere. According to the method, the dispersity of metal components in pore channels of the molecular sieve is improved by utilizing ultrasonic-assisted impregnation, high CO conversion rate and high liquid fuel (C5 < + >) selectivity are realized under the condition of low-hydrogen-carbon-ratio synthesis gas by regulating and controlling the acidity of the carrier and the Fe-Co bimetallic synergistic effect, and meanwhile, the generation of byproducts such as methane and carbon dioxide is remarkably inhibited. The catalyst is simple in preparation process and high in mechanical strength, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to a catalyst for the direct conversion of syngas into liquid fuels, its preparation method and application, and particularly to a ZSM-5 molecular sieve-supported iron-cobalt bimetallic catalyst suitable for low hydrogen-to-carbon ratio syngas, with high selectivity for liquid fuels and low selectivity for carbon dioxide, its preparation method and application, belonging to the fields of coal chemical and new energy chemical technology. Background Technology

[0002] With the increasing scarcity of global oil resources and the continuous growth of energy demand, utilizing abundant non-oil carbon resources such as coal and biomass to produce syngas (CO+H2) through gasification, and then converting it into high-value-added liquid fuels, is an important way to alleviate the contradiction between oil supply and demand and ensure energy security.

[0003] Fischer-Tropsch synthesis is a core technology for producing liquid fuels from syngas, with traditional catalysts primarily being iron-based and cobalt-based. While cobalt-based catalysts exhibit good activity, they typically require a high hydrogen-to-carbon ratio (H2 / CO=2) and are subject to stringent requirements on feedstock purity. Iron-based catalysts, although suitable for syngas with low hydrogen-to-carbon ratios (H2 / CO=1) derived from coal or biomass gasification, often involve intense water-gas shift reactions (WGS), leading to significant carbon dioxide (CO2) generation. This not only reduces carbon resource utilization efficiency but also increases carbon emissions. Furthermore, the product distribution of traditional Fischer-Tropsch synthesis follows the Anderson-Schulz-Flory (ASF) statistical law, resulting in a broad carbon chain distribution that limits the selectivity for target liquid fuels, and often involves the generation of a high proportion of the byproduct methane (CH4).

[0004] To overcome the limitations of ASF distribution, researchers have recently attempted to couple metal components with shape-selective zeolite molecular sieves (such as ZSM-5) to construct bifunctional catalysts, utilizing the pore confinement and acidic sites of the molecular sieves to regulate product distribution. However, under low hydrogen-to-carbon ratio reaction conditions, existing catalyst systems often struggle to simultaneously achieve high activity and high selectivity for the target product, commonly exhibiting problems such as high methane selectivity, high CO2 emissions, or insufficient liquid fuel yield.

[0005] Therefore, developing a catalyst that can adapt to low hydrogen-to-carbon ratio (H2 / CO=1) conditions, while having high liquid fuel yield and selectivity, and significantly suppressing the generation of methane and carbon dioxide, is of great practical significance for improving the economic and environmental benefits of syngas conversion. Summary of the Invention

[0006] Objectives of the Invention: Addressing the problems of low metal component dispersion, uneven distribution of active sites, and difficulty in precisely controlling the acidic structure of the support in existing ZSM-5 supported iron-cobalt-based catalysts, one objective of this invention is to provide an FeCo-based catalyst based on ZSM-5 with different Si / Al ratios. Another objective is to provide a method for preparing this catalyst. This method significantly improves the dispersion of the metal component within the molecular sieve channels by employing ultrasonic-assisted impregnation technology. Simultaneously, by controlling the Si / Al ratio of the ZSM-5 support, the surface acid density and pore structure properties of the catalyst are effectively adjusted, thereby obtaining a structurally stable, high-performance catalyst with suitable metal-support interactions. A final objective of this invention is to provide the application of this catalyst in the direct conversion of syngas to liquid fuels, particularly its application in the preparation of liquid fuels at low hydrogen-to-carbon ratios.

[0007] Technical solution: The present invention discloses an FeCo / ZSM-5 catalyst, wherein the FeCo / ZSM-5 catalyst comprises a ZSM-5 molecular sieve with a specific silicon-to-aluminum ratio as a support, the pores of the ZSM-5 molecular sieve being loaded with active components iron and cobalt, wherein the silicon-to-aluminum ratio of the ZSM-5 molecular sieve is 30~170, and during preparation, the mass ratio of ZSM-5 molecular sieve to the total mass of iron and cobalt is 100:21, wherein the mass ratio of iron to cobalt is 1:1.5~1:3, preferably 1:2.

[0008] A method for preparing the FeCo / ZSM-5 catalyst of the present invention includes the following steps:

[0009] Option 1: Dissolve the iron and cobalt sources in an alcohol solution, add ZSM-5 molecular sieve, ultrasonically treat, dry, calcine at high temperature under an inert atmosphere, and cool.

[0010] or:

[0011] Option 2: Dissolve the iron source in an alcohol solution, add ZSM-5 molecular sieve, ultrasonically treat, dry, add cobalt source in an alcohol solution, continue ultrasonic treatment, continue drying, calcine at high temperature under an inert atmosphere, and cool.

[0012] or:

[0013] Option 3: Dissolve the cobalt source in an alcohol solution, add ZSM-5 molecular sieve, ultrasonically treat, dry, add an iron source in an alcohol solution, continue ultrasonic treatment, continue drying, calcine at high temperature under an inert atmosphere, and cool.

[0014] Furthermore, in the above three schemes, the iron source is a soluble inorganic or organic salt of iron, and the cobalt source is a soluble inorganic or organic salt of cobalt. Preferably, the soluble inorganic salt of iron is selected from ferric nitrate nonahydrate, the soluble organic salt of iron is selected from ferric citrate or ferric oxalate, the soluble inorganic salt of cobalt is selected from cobalt nitrate hexahydrate, and the soluble organic salt of cobalt is selected from cobalt citrate or cobalt oxalate.

[0015] Furthermore, the silicon-aluminum ratio (SiO2 / Al2O3) of the ZSM-5 molecular sieve is 30~170; preferably 50~70, more preferably 70.

[0016] Furthermore, in the above three schemes, the alcohol solution is one or more of ethanol, methanol or isopropanol, preferably ethanol; the amount of alcohol solution used is 20~60mL of alcohol solution per 1g ZSM-5 molecular sieve, preferably 30~50mL.

[0017] Furthermore, in Scheme 1, the ultrasonic treatment time is 2-6 hours, preferably 3-5 hours; in Scheme 2 and Scheme 3, the ultrasonic treatment and the continued ultrasonic treatment time are both 2-6 hours.

[0018] Furthermore, in the above three schemes, the drying and continued drying temperatures are both 50~90℃, preferably 60~80℃, and the drying and continued drying times are both 6 hours or more.

[0019] Furthermore, the inert atmosphere is one or more of nitrogen, argon, or helium; the high-temperature calcination temperature is 400~600℃, preferably 500℃; and the high-temperature calcination time is 4~8 h, preferably 5~7 h.

[0020] The present invention also includes the application of the FeCo / ZSM-5 catalyst in the direct conversion of syngas to liquid fuels.

[0021] Furthermore, the application includes the following steps:

[0022] The FeCo / ZSM-5 catalyst was loaded into the reactor and in-situ reduced and activated for 6–10 hours under a hydrogen atmosphere, at 350–450 °C and 0.1–2.0 MPa. After activation, the reaction temperature was adjusted to 220–260 °C and the reaction pressure to 1.5–2.5 MPa. Syngas with a hydrogen-to-carbon molar ratio (H₂ / CO) of 0.5–1.5 was introduced, and the reaction was carried out at a gas space velocity of 2000–6000 h⁻¹. -1 The reaction takes place under specific conditions.

[0023] This invention reveals that the silica-to-alumina ratio of the ZSM-5 molecular sieve support is a key factor affecting catalyst performance. The silica-to-alumina ratio directly determines the density and strength of Brønsted acidic sites within the molecular sieve framework. When the silica-to-alumina ratio is too low (e.g., <30), the acid density on the support surface is too high, and these acidic sites catalyze intense secondary cracking reactions in intermediates. This leads to a significant increase in the selectivity for methane and short-chain alkanes (C2-C4) in the products, drastically reducing the selectivity for the target liquid fuel (C4). 5+ The yield of CO is affected by the high silicon-to-aluminum ratio (e.g., >350). When the silicon-to-aluminum ratio is too high (e.g., >350), acidic sites are scarce, weakening the catalyst's hydrocracking and isomerization capabilities, leading to severe product weighting, and the weak metal-support interaction is detrimental to the dispersion of active components. The preferred silicon-to-aluminum ratio range of this invention (30~170) creates a suitable acidic environment, ensuring high CO conversion activity while effectively suppressing over-cracking by utilizing appropriate pore confinement and acid catalysis, thereby achieving high liquid fuel selectivity under low hydrogen-to-carbon ratio conditions.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0025] (1) With the synergistic effect of Fe-Co bimetallic catalyst and the precise control of the acidity of the support, this invention achieves highly selective directional synthesis of liquid hydrocarbon products while maintaining high reactivity, and significantly suppresses the generation of by-products such as methane and carbon dioxide.

[0026] (2) The preparation process of this invention is simple and the raw materials are widely available. The ultrasonic-assisted impregnation method significantly improves the dispersion and utilization rate of metal components in the carrier channels.

[0027] (3) The catalyst of the present invention has excellent mechanical strength and structural stability. It can maintain stable performance under a wide range of temperature and pressure conditions and has good repeatability, and has good prospects for industrial application. Attached Figure Description

[0028] Figure 1 Here is a SEM image of the catalyst 1Fe2Co / ZSM-5(70) prepared in Example 2;

[0029] Figure 2 These are performance evaluation graphs of the catalysts prepared in Examples 1-12 and Comparative Examples 1-3;

[0030] Figure 3 This is a stability diagram of the 2Co+1Fe / ZSM-5(70) catalyst. Detailed Implementation

[0031] To facilitate understanding of the present invention, the technical solution of the present invention will be further described below with reference to specific drawings and embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0032] Example 1 Preparation of catalyst 1Fe3Co / ZSM-5(70)

[0033] 0.379 g of ferric nitrate nonahydrate and 0.777 g of cobalt nitrate hexahydrate were weighed and dissolved in 40 mL of ethanol to form a mixed solution. 1 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 70 (Si / Al=70) was weighed and added to the mixed solution. The mixed solution was ultrasonically treated for 4 hours, dried at 70°C for 6 hours, and then calcined at 500°C for 6 hours under an argon atmosphere to obtain the 1Fe3Co / ZSM-5(70) catalyst.

[0034] Example 2 Preparation of catalyst 1Fe2Co / ZSM-5(70)

[0035] 0.5050 g of ferric nitrate nonahydrate and 0.6905 g of cobalt nitrate hexahydrate were weighed and dissolved in 40 mL of ethanol to form a mixed solution. 1 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 70 (Si / Al=70) was weighed and added to the mixed solution. The mixed solution was ultrasonically treated for 4 hours, dried at 70°C for 6 hours, and then calcined at 500°C for 6 hours under an argon atmosphere to obtain the 1Fe2Co / ZSM-5(70) catalyst.

[0036] The catalyst 1Fe2Co / ZSM-5(70) prepared in this embodiment was analyzed by scanning electron microscopy, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the 1Fe2Co / ZSM-5(70) catalyst has a regular polyhedral shape.

[0037] Example 3 Preparation of 1Fe1.5Co / ZSM-5(70)

[0038] 0.606 g of ferric nitrate nonahydrate and 0.621 g of cobalt nitrate hexahydrate were weighed and dissolved together in 40 mL of ethanol. 1 g of ZSM-5 (Si / Al=70) molecular sieve was added. The above solution was ultrasonically treated for 4 hours and then dried at 70°C for 6 hours. Then it was calcined at 500°C for 6 hours under argon atmosphere to obtain 1Fe1.5Co / ZSM-5(70) catalyst.

[0039] Example 4 Preparation of catalyst 1Fe1Co / ZSM-5(70)

[0040] 0.7575 g of ferric nitrate nonahydrate and 0.5177 g of cobalt nitrate hexahydrate were weighed and dissolved together in 40 mL of ethanol. 1 g of ZSM-5 (Si / Al=70) molecular sieve was added. The above solution was ultrasonically treated for 4 hours and then dried at 70°C for 6 hours. Then it was calcined at 500°C for 6 hours under argon atmosphere to obtain 1Fe1Co / ZSM-5(70) catalyst.

[0041] Example 5 Preparation of catalyst 2Fe1Co / ZSM-5(70)

[0042] 1.010 g of ferric nitrate nonahydrate and 0.345 g of cobalt nitrate hexahydrate were weighed and dissolved together in 40 mL of ethanol. 1 g of ZSM-5 (Si / Al=70) molecular sieve was added. The solution was ultrasonically treated for 4 hours and then dried at 70°C for 6 hours. Then it was calcined at 500°C for 6 hours under an argon atmosphere to obtain the 2Fe1Co / ZSM-5(70) catalyst.

[0043] Example 6 Preparation of catalyst 1Fe2Co / ZSM-5(30)

[0044] 0.505 g of ferric nitrate nonahydrate and 0.6905 g of cobalt nitrate hexahydrate were weighed and dissolved together in 40 mL of ethanol. 1 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30 (Si / Al=30) was added to the above solution. The solution was ultrasonically treated for 4 hours, dried at 70°C for 6 hours, and then calcined at 500°C for 6 hours under an argon atmosphere to obtain the 1Fe2Co / ZSM-5(30) catalyst.

[0045] Example 7 Preparation of catalyst 1Fe2Co / ZSM-5(50)

[0046] 0.505 g of ferric nitrate nonahydrate and 0.6905 g of cobalt nitrate hexahydrate were weighed and dissolved together in 40 mL of ethanol. 1 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 50 (Si / Al=50) was added. The above solution was ultrasonically treated for 4 hours and then dried at 70°C for 6 hours. Then it was calcined at 500°C for 6 hours under an argon atmosphere to obtain the 1Fe2Co / ZSM-5(50) catalyst.

[0047] Example 8 Preparation of catalyst 1Fe2Co / ZSM-5(170)

[0048] 0.5050 g of ferric nitrate nonahydrate and 0.6905 g of cobalt nitrate hexahydrate were weighed and dissolved together in 40 mL of ethanol. 1 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 170 (Si / Al=170) was added. The above solution was ultrasonically treated for 4 hours and then dried at 70°C for 6 hours. Then it was calcined at 500°C for 6 hours under an argon atmosphere to obtain the 1Fe2Co / ZSM-5(170) catalyst.

[0049] Example 9 Preparation of 1Fe2Co / ZSM-5 (350~400) catalyst:

[0050] 0.5050 g of ferric nitrate nonahydrate and 0.6905 g of cobalt nitrate hexahydrate were weighed and dissolved together in 40 mL of ethanol. 1 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 350-400 (Si / Al=400) was added. The above solution was ultrasonically treated for 4 hours and then dried at 70°C for 6 hours. Then it was calcined at 500°C for 6 hours under an argon atmosphere to obtain the 1Fe2Co / ZSM-5 (350-400) catalyst.

[0051] In Examples 2 and 6-9, ZSM-5 molecular sieves with silica-to-alumina ratios of 70, 30, 50, 170, and 350-400 were selected to investigate the regulatory effect of different acid densities on the distribution of Fischer-Tropsch synthesis products. Specifically, Example 6 had a silica-to-alumina ratio of 30 to simulate reaction behavior under high acid strength conditions, Example 2 had a silica-to-alumina ratio of 70 to simulate reaction behavior under moderate acid strength conditions, and Example 9 had a high silica-to-alumina ratio to investigate reaction behavior under low acid strength conditions.

[0052] Example 10 Preparation of catalyst 1Fe+2Co / ZSM-5(70)

[0053] First, 0.6905g of cobalt nitrate hexahydrate was dissolved in 40ml of ethanol, and 1g of ZSM-5 (Si / Al=70) molecular sieve was added. The mixture was ultrasonically treated for 4 hours, and then dried at 70°C for 6 hours. The dried solid was then added to an ethanol solution containing 0.505g of ferric nitrate nonahydrate (0.505g ferric nitrate nonahydrate: 40ml ethanol). The mixture was ultrasonically treated again for 4 hours and then dried for 6 hours. Finally, the solid was calcined at 500°C for 6 hours under an argon atmosphere to obtain the 1Fe+2Co / ZSM-5(70) catalyst.

[0054] Example 11 Preparation of catalyst 2Co+1Fe / ZSM-5(70)

[0055] First, 0.505g of ferric nitrate nonahydrate was dissolved in 40ml of ethanol, and 1g of ZSM-5 (Si / Al=70) molecular sieve was added. The mixture was ultrasonically treated for 4 hours, and then dried at 70°C for 6 hours. The dried solid was then added to an ethanol solution containing 0.6905g of cobalt nitrate nonahydrate (0.6905g cobalt nitrate nonahydrate: 40ml of ethanol). The mixture was ultrasonically treated again for 4 hours and then dried for 6 hours. Finally, the solid was calcined at 500°C for 6 hours under an argon atmosphere to obtain the 2Co+1Fe / ZSM-5(70) catalyst.

[0056] Example 12

[0057] The preparation process is the same as in Example 2, except that the high-temperature calcination temperature is set to 300℃, 400℃, 600℃ and 800℃ respectively, to obtain catalysts 1Fe2Co / ZSM-5(70)-300℃, 1Fe2Co / ZSM-5(70)-400℃, 1Fe2Co / ZSM-5(70)-600℃ and 1Fe2Co / ZSM-5(70)-800℃.

[0058] Comparative Example 1: Preparation of the single-metal catalyst Fe / ZSM-5(70)

[0059] 1.515g of ferric nitrate nonahydrate was dissolved in 40ml of ethanol, and 1g of ZSM-5 (Si / Al=70) molecular sieve was added. The solution was sonicated for 4 hours and then dried at 70°C. Finally, it was calcined at 500°C for 6 hours under an argon atmosphere to obtain the Fe / ZSM-5(70) catalyst.

[0060] Comparative Example 2: Preparation of the single-metal catalyst Co / ZSM-5(70)

[0061] 1.0355 g of cobalt nitrate hexahydrate was dissolved in 40 ml of ethanol, and 1 g of ZSM-5 (Si / Al=70) molecular sieve was added. The solution was sonicated for 4 hours and then dried at 70°C. Finally, it was calcined at 500°C for 6 hours under an argon atmosphere to obtain the Co / ZSM-5 (70) catalyst.

[0062] Comparative Example 3

[0063] The preparation process is the same as in Example 2, except that the catalyst 1Fe2Co / ZSM-5(70)-Air is prepared by calcination in an air atmosphere.

[0064] Catalyst performance evaluation:

[0065] (1) 0.5 g of the catalysts prepared in Examples 1-12 and Comparative Examples 1-3 were respectively loaded into a fixed-bed reactor and reduced for 8 hours at 2 MPa, 400°C, and H2 flow rate of 30 mL / min. Then the temperature was lowered to 240°C, the pressure was maintained at 2 MPa, and syngas with H2 / CO = 1 (containing 20% ​​N2) was introduced at a space velocity of 4800 h⁻¹. -1 The reaction proceeded. The reaction performance of the prepared catalyst was evaluated, and the test results are shown in Table 1 and... Figure 2 As shown.

[0066] Meanwhile, the performance results of the catalyst prepared in Example 2 under different experimental conditions, with a synthesis gas (H2 / CO) ratio of 0.5 and 1.5, are summarized in Table 1.

[0067] Table 1. Performance of the catalysts prepared in Examples 1-12 and Comparative Examples 1-3 for CO hydrogenation reaction.

[0068]

[0069] Note:

[0070] As shown in Table 1, comparing Examples 2 with Examples 6-9, it is evident that in Example 6, the Si / Al ratio in the ZSM-5 molecular sieve is 30. Due to the excessive number of acidic sites in the ZSM-5 molecular sieve, over-cracking occurs. Although the conversion rate is still acceptable, the methane selectivity is significantly increased (28.5%), and the target product C... 5+ The Si / Al ratio in the ZSM-5 molecular sieves of Examples 8 and 9 is increased, and the acidic sites are reduced, especially with Si / Al ratios of 350-400. This weakens the catalyst's hydrocracking and isomerization capabilities, resulting in severe product weighting. Furthermore, the reduced acidic sites lead to weak metal-support interactions, which are detrimental to the dispersion of active components.

[0071] Comparing Example 2 with Comparative Example 3, Comparative Example 3 uses air roasting. Because oxygen in the air is involved, it usually leads to the formation of large particles of Co3O4 and Fe2O3, which are difficult to reduce, so the CO conversion rate is low (18.5%).

[0072] Comparing Example 2 and Example 12, in Example 12, calcination at 300℃ resulted in incomplete decomposition of nitrates due to the low temperature, leading to pore blockage and extremely low activity. Calcination at 800℃, on the other hand, caused the molecular sieve framework to collapse or metal to severely agglomerate (sinter), almost resulting in deactivation. Experiments ultimately revealed that a calcination temperature of 400-600℃ was suitable, with 500℃ showing the most outstanding performance.

[0073] Depend on Figure 2It can be seen that the catalysts 1Fe+2Co / ZSM-5(70), 1Fe2Co / ZSM-5(70), and 2Co+1Fe / ZSM-5(70) exhibit superior Fischer-Tropsch synthesis performance, with CO conversion rates exceeding 30%, while the target product C... 5+ Selectivity is above 64%, especially for 1Fe2Co / ZSM-5(70) and 2Co+1Fe / ZSM-5(70) C 5+ The selectivity is above 75%.

[0074] (2) Stability of catalyst 2Co+1Fe / ZSM-5(70)

[0075] The results are as follows Figure 3 As shown, by Figure 3 It can be seen that the CO conversion rate of the 2Co+1Fe / ZSM-5(70) catalyst did not decrease significantly after 40h.

Claims

1. A FeCo / ZSM-5 catalyst, characterized in that, The FeCo / ZSM-5 catalyst comprises ZSM-5 molecular sieve with a specific silicon-to-aluminum ratio as a support. The ZSM-5 molecular sieve has active components iron and cobalt loaded in its pores. The silicon-to-aluminum ratio of the ZSM-5 molecular sieve is 30~170. During preparation, the mass ratio of ZSM-5 molecular sieve to total iron and cobalt is 100:21, and the mass ratio of iron to cobalt is 1:1.5~1:

3.

2. A method for preparing the FeCo / ZSM-5 catalyst according to claim 1, characterized in that, Includes the following steps: Option 1: Dissolve the iron and cobalt sources in an alcohol solution, add ZSM-5 molecular sieve, ultrasonically treat, dry, calcine at high temperature under an inert atmosphere, and cool. or: Option 2: Dissolve the iron source in an alcohol solution, add ZSM-5 molecular sieve, ultrasonically treat, dry, add cobalt source in an alcohol solution, continue ultrasonic treatment, continue drying, calcine at high temperature under an inert atmosphere, and cool. or: Option 3: Dissolve the cobalt source in an alcohol solution, add ZSM-5 molecular sieve, ultrasonically treat, dry, add an iron source in an alcohol solution, continue ultrasonic treatment, continue drying, calcine at high temperature under an inert atmosphere, and cool.

3. The preparation method according to claim 2, characterized in that, The iron source is a soluble inorganic or organic salt of iron; the cobalt source is a soluble inorganic or organic salt of cobalt.

4. The preparation method according to claim 3, characterized in that, The soluble inorganic salts of iron are selected from ferric nitrate nonahydrate, and the soluble organic salts of iron are selected from ferric citrate or ferric oxalate. The soluble inorganic salts of cobalt are selected from cobalt nitrate hexahydrate, and the soluble organic salts of cobalt are selected from cobalt citrate or cobalt oxalate.

5. The preparation method according to claim 2, characterized in that, The alcohol solution is one or more of ethanol, methanol or isopropanol; the amount of alcohol solution used is 20~60mL of alcohol solution per 1g of ZSM-5 molecular sieve.

6. The preparation method according to claim 2, characterized in that, In Scheme 1, the ultrasonic treatment time is 2-6 hours; in Scheme 2 and Scheme 3, the ultrasonic treatment and the continued ultrasonic treatment time are both 2-6 hours.

7. The preparation method according to claim 2, characterized in that, The drying and continued drying temperatures are both 50~90℃, and the drying and continued drying times are both more than 6 hours.

8. The preparation method according to claim 2, characterized in that, The inert atmosphere is one or more of nitrogen, argon or helium; the high-temperature calcination temperature is 400~600℃, and the high-temperature calcination time is 4~8h.

9. The application of the FeCo / ZSM-5 catalyst according to claim 1 in the direct conversion of syngas to liquid fuels.

10. The application according to claim 10, characterized in that, The application includes the following steps: The FeCo / ZSM-5 catalyst was loaded into the reactor and in-situ reduced and activated for 6–10 h under a hydrogen atmosphere, at 350–450 °C and 0.1–2.0 MPa. After activation, the reaction temperature was adjusted to 220–260 °C and the reaction pressure to 1.5–2.5 MPa, and syngas with a hydrogen-to-carbon molar ratio (H₂ / CO) of 0.5–1.5 was introduced at a gas space velocity of 2000–6000 h⁻¹. -1 The reaction takes place under specific conditions.

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